An Efficient Hybrid Key Exchange Mechanism

TL;DR

The paper introduces extsc{CHOKE}, a hybrid key exchange mechanism that efficiently transmits multiple session keys simultaneously using code-based encoding, reducing costs while maintaining security.

Contribution

It proposes a novel code-based hybrid KEM that enables secure multi-key transmission with optimal communication cost and improved efficiency over traditional methods.

Findings

Achieves computational individual security for multiple keys.

Reduces computational and communication costs by an n-fold factor.

Proves optimality of communication cost under certain conditions.

Abstract

We present \textsc{CHOKE}, a novel code-based hybrid key-encapsulation mechanism (KEM) designed to securely and efficiently transmit multiple session keys simultaneously. By encoding $n$ independent session keys with an individually secure linear code and encapsulating each resulting coded symbol using a separate KEM, \textsc{CHOKE} achieves computational individual security -- each key remains secure as long as at least one underlying KEM remains unbroken. Compared to traditional serial or combiner-based hybrid schemes, \textsc{CHOKE} reduces computational and communication costs by an $n$-fold factor. Furthermore, we show that the communication cost of our construction is optimal under the requirement that each KEM must be used at least once.